Whenever there is relative movement between a fluid and a body, the fluid exerts a force on the body in the direction of relative movement between the fluid and the body. This force is known as drag.
When the body is a vehicle, such as an automobile, a train, a watercraft, an aircraft or some other type of vehicle, drag is always present and opposes to some extent the motion of the vehicle. For instance, when the fluid through which a vehicle moves is air, the air exerts a drag on the vehicle that opposes the motion of the vehicle. In particular, the drag exerted on the vehicle is greatest when the wind direction is opposite to the direction of motion of the vehicle. Thus, the air moving relative to the vehicle, and particularly the wind, is characterized by an important amount of energy that opposes the motion of the vehicle.
Devices have been developed to extract energy from fluids moving relative to the devices and to convert the extracted energy into mechanical or electrical energy. Typically, however, existing devices inefficiently expend some of the extracted energy as a result of their design and leave room for improvement. Furthermore, existing devices are typically part of stationary energy generators and have not been successfully applied to vehicles for allowing extraction of energy from fluids through which the vehicles move, while not increasing drag forces applied on the vehicles.
Accordingly, there is a need for an improved device for interacting with a fluid moving relative to the device and which can be used in a vehicle or in a stationary energy generator.